Luggage and bags:
I would suggest you to carry little luggage because here you can find almost everything and for very cheap prices.
Clothing/Shoes/Weather Gear: The climate is temperate so it depandes on the season. The winter usually is very cold and the summer often very hot.
Toiletries and Medical Supplies: There are plenty of drug-stores here so I believe you can find almost everything you'd need.
Photo Equipment: A camera would be enough.
Luggage and bags: Many tourists when coming in Bulgaria for a first time think that they should bring lots of things with them. I would say this is a major mistake. I have seen people coming with even bottels of water in their bags! Which is really silly. Actually, here you can find everything you need at very low prices. Pack a few clothes, some very comfortable shoes and your camera. That is far enough!
Luggage and bags:
Pack as light as possible to avoid theft possibilities. Of course, this applies everywhere in the world.
Clothing/Shoes/Weather Gear: Bulgaria is very temperate. Hot summers, cold winters. Dress as if you were going to Denver--the climate is almost identical. And do expat Americans everywhere a favor and try not to dress in the loudest day-glo outfits you can find.
Smooth pavement is almost unknown, so wear shoes with sturdy heels/soles.
Dry cleaning is iffy at best and public laundromats do not exist.
Toiletries and Medical Supplies: You can get just about anything you want if you're not too picky about brand names. Most medications exist here but have different names, so take enough of your own to last the trip. Feminine products are easy to find but (I'm told) are not quite top-of-the-line. Sofia's water is potable if not particularly tasty (the bottled water's fine), so decontaminizers are not necessary unless you're going camping.
Photo Equipment: Everything's available but, unlike most products here, are slightly more expensive than in America.
Camping/Beach/Outdoor Gear: Most everything's available for rental or purchase.
Miscellaneous: Electricity's 220 volt 50 Hz, so bring necessary adapters for electrical devices. Plugs are twin round prongs.
Luggage and bags:
I prefer to travel light no matter which means of transportation I get. One bag plus one hand luggage should be sufficient for a trip. There is a reason for it -- you are more prone to inspection by customs if you have lots of luggage. (Don't do like my brothers who few years ago went home w/ 7 suitcases and said he had nothing to declare! It took us a week to clear customs)... in other words, make sure you do not look economically viable for the customs officers...;-)))
Clothing/Shoes/Weather Gear: Clothing depends on the season. We have four distinct seasons. Winters are cold (in the minus but not often less than minus 10-15 centigrade), summers are hot (30 and above). Spring and Autumn are temperate and you can get showers.
Winter -- make sure you have enough socks, gloves, shawls and hats. Boots are a must even if it is dry cold.
Summer -- rarely, you'll need anything w/ long sleeve so don't take more than one (unless it is like this summer, which is very unusually cold).
Toiletries and Medical Supplies: You should be able to get everything in the Pharmacies. If you bring prescriptions, make sure they have the latin names of the medicines (not the brand names). There are plenty of private medical and dental cliniques and offices, but if needed, ask your hotel/host for help (you'll most probably have to pay for the visit).
Emergency is only one -- Pirogov (it's big) and is for free.
Photo Equipment: Unless something super fancy, you should be able to get your batteries, chargers, etc., in case you need. The fancies the equipment, the fancier the prices, tho'. The plugs are like in Continental Europe.
If you visit Sofia of greatest importancy is to pick your ... camera :)))
Otherwise you'll be very sorry :) really